The use of targeted additional funding for school-age education, intended to improve student attainment, is a widespread phenomenon internationally. It is slightly rarer that the funding is used to improve attainment specifically for the most disadvantaged students – often via trying to attract teachers to poorer areas, or encouraging families to send their children to school. It is even rarer that funding is used to try and reduce the attainment gap between economically disadvantaged students and their peers, and almost unheard for the funding to be intended to change the nature of school intakes by making disadvantaged students more attractive to schools. These last two were the objectives set for Pupil Premium funding to schools in England. The funding started in 2011, for all state-funded schools at the same time, so there is no easy counterfactual to help assess how effective it has been. The funding is a considerable investment every year and it is therefore important to know whether it works as intended. This paper presents a time series analysis of all students at secondary school in England from 2006, well before the funding started, until 2019, the most recent year for which there are attainment figures. It overcomes concerns that the official attainment gap between students labelled disadvantaged and the rest is sensitive to demographic, economic, legal and other concurrent policy changes. It does this by looking at a stable group of long-term disadvantaged students. It is argued that this group would have attracted Pupil Premium funding if it had existed in any year and under any economic conditions. After 2010, these long-term disadvantaged pupils became substantially less clustered in specific schools in their first year and throughout their remaining school life. This improvement cannot be explained by economic or other factors used in this paper, and so it looks as though the Pupil Premium has been effective here. The picture for the attainment gap at age 16 is more mixed. It is partly confused by changes in the grading of assessments in 2014 and again from 2016. The reasons why the improvements are less clear than at primary school are discussed, and they involve the nature of evidence available to secondary schools to help them improve the attainment of their most disadvantaged students.